The Centers for Medicare and Medicaid Services lowered the Medicare Star quality ratings for Centene Corp. unit Health Net of California Inc.'s Medicare Advantage plan to 3.5 from 4.0 for the 2018 rating year.

The reduction was the result of a penalty associated with a plan audit in 2015, Centene said in a news release. The penalty will only impact the 2018 rating year and will not have a continuing impact on the Star ratings in future rating years. Centene said it intends to appeal the application of the penalty.

The downgrade of Health Net's rating will lower Centene's parent 2018 Star rating to 3.5 from 4.0, the company said.

Separately, Anthem Inc. announced improved Medicare Star ratings for its Medicare Advantage health plan affiliates.

Heading into 2018, more than 60% of the Medicare Advantage members in Anthem's affiliated health plans will be enrolled in plans rated four stars or better. At least one of these health plans will be rated five stars by CMS, the company said. Anthem's affiliates will be offering five-star preferred provider organization plans in the New Hampshire, Georgia and Kentucky markets.

The 2018 rating year will affect quality bonus payments for Medicare Advantage plans in 2019.